This application claims the priority of German Application No. 199 50 259.5 filed Oct. 18, 1999, which is incorporated herein by reference.
The invention relates to a compound needle, having the features as defined in the preamble to patent claim 1 or patent claim 2.
Compound needles, such as the ones used for flat knitting machines or circular knitting machines, consist of a needle member with a closing element channel, inside of which a closing element is positioned such that it can be displaced. A needle head in the form of a hook is formed onto the free end of the needle member. The hook can be opened or closed by the closing element. The knitting machine comprises at least one flat or one cylinder-shaped and/or one plate-shaped needle bed containing respectively several needle channels. The compound needles are arranged inside these needle channels such that they can be displaced in longitudinal direction, wherein they perform a back-and-forth movement in longitudinal direction during the knitting operation. The closing element must perform a coordinated back-and-forth movement, for which it is provided with a so-called butt that functions as a means for transmitting movement and makes contact with curved surfaces. Curved surfaces of this type are, for example, the flanks of a so-called cam channel.
During the knitting operation, the head as well as the closing element of the compound needle come in contact with the yarn. As a result, dust or filament particles can be deposited on the closing element, depending on the composition of the yarn as well as the amount of dirt that is carried along. For example, if wool is used for the knitting, dust particles clinging to the wool, salt crystals stemming from the washing of the wool, sand or short filaments can be deposited on the closing element. As a result of the back-and-forth movement of the closing element, these particles can reach the closing element channel and lead to difficulties.
A compound needle of this type with divided closing element is known from U.S. Pat. No. 1,673,634. The closing element is composed of two connected closing element springs, which respectively push past the hook of the compound needle on the side and are spread apart in this way.
The arrangement of the compound needle disclosed in German Published Application 44 30 705, to which corresponds British Patent No. 2,292,953, is similar. The closing element in this case is also formed by two closing element springs, which are spread apart by moving past the hook on the side, thereby making it possible for dirt to be deposited between the closing element springs.
The same is true for the compound needle according to European Patent 08 75 614 to which corresponds U.S. Pat. No. 5,937,673. The compound needle comprises a needle member with needle channel, inside of which a closing element is guided. The closing element consists of a closing element base member that holds two closing element springs, which are designed to be symmetrical relative to each other. The needle hook periodically spreads apart the closing element springs during the operation, thereby allowing dirt and fiber residues to reach the gap defined between the closing element springs.
German Unexamined Patent Application 21 46 981 furthermore discloses a needle base member for a compound needle, which has a closing element channel with rear openings. The two walls on the side of the closing element channel are formed continuously, without openings, and between them limit the closing element channel. The closing element guided therein has elongated holes through which guide pins extend. The guide pins are respectively anchored in the side walls of the closing element. The closing element has a one-piece design.
German Published Patent Application 31 23 785 discloses another known compound needle. The known compound needle comprises a closing element divided into two closing element springs, which are designed to be symmetrical relative to each other. The closing element is arranged inside a compound needle closing element channel that is closed on three sides. An opening in the form of an elongated hole through which a guide pin extends is provided for guiding the closing element.
The problem with this as well as most of the previously mentioned compound needles is that dirt can reach the area between the two closing element springs. If that case occurs, it can lead to a gradual spreading apart of the closing element springs inside the closing element channel, so that with increasing amounts of dirt, the closing element can only be moved with difficulty inside the channel. In turn, this leads to increased friction and wear. In the extreme case where the closing element is extremely hard to move or is wedged inside the channel, the loop formation, the loop transfer and the loop knockover are obstructed. Given another extreme case, the closing elements can no longer be moved inside the closing element channel of the needle member, so that a butt break occurs.
Based on this assumption, it is the object of the invention to create a compound needle with little tendency to accumulate dirt.
This object is solved alternately with the compound needle according to claim 1 or the compound needle according to claim 2.
Both solutions have in common that the divided closing element is not as likely to become wedged in as a result of stress caused by dirt. The closing element channel contains at least one area in which fiber residues can accumulate without causing the closing element springs to spread apart. According to claim 1, the closing element springs are designed to be asymmetrical relative to each other. It means that they can overlap only partially in the closing element channel and thus do not fill out parts of the channel, which by itself creates additional buffer space in the closing element channel for holding foreign matter. Thus, a wedging in of the closing element is less likely and does not occur as quickly. In addition, the closing element channel is advantageously open on the side, meaning at least one of the channel sidewalls is provided with an opening or clearance. Alternatively or in addition, one or more openings can be provided in the bottom of the closing element channel. The opening on the side can be formed as a cutout in the closing element channel wall. Owing to the relative movement between closing element and needle base member, deposits that can reach the closing element channel wall because of the asymmetry of the two closing element springs can be moved through these openings or clearances into the needle channel. They are removed from the needle channel as a result of the relative movement between the compound needle and the needle channel.
The compound needle according to claim 2 is also based on this principle. Openings in the closing element springs initially permit deposits that have accumulated between the closing element springs to move from the gap formed between the closing element springs to the closing element channel walls and through the openings in these walls to the outside.
By preventing deposits that have accumulated between the closing element springs from forcedly spreading apart the closing element springs and wedge them against the closing element channel walls, the easy movement of the compound needle is maintained continuously, even if yarns with relatively high dirt loads must be processed. The compound needle according to the invention thus proves to have little tendency to accumulate dirt.
It is advantageous if the compound needles contain openings, which are arranged at different locations on the two closing element springs. The openings simultaneously create areas for holding and moving through the dirt that has entered the closing element channel, thus preventing dirt from being wedged between the closing element springs. In part, this also applies if the openings are arranged such that they overlap in some areas. The overlapping of the openings minimizes regions between the closing element springs, in which dirt could settle and spread apart the closing element springs.
One advantageous embodiment of the compound needle comprises a multi-part closing element, composed of a closing element member and closing element springs. These parts (closing element springs and closing element base member) can be rigidly connected or such that they can be detached. The closing element springs comprise web areas and web sections that extend in longitudinal direction of the channel, are displaced relative to each other and preferably do not overlap. With these, the above-mentioned advantages are realized to a particular degree. The web areas and web sections preferably extend through the closing element channel and are guided on the side by the channel sidewalls. The web sections change to guide sections for a guidance parallel to the closing element walls. These guide sections are preferably displaced relative to each other in longitudinal direction to prevent dirt from accumulating between the guide sections.
In addition, the closing element springs can also be designed asymmetrical between the guide sections and a respective loop-support section, which also leads to a reduced tendency for accumulating dirt and being wedged in. The closing element springs thus for the most part are not designed to overlap.
It is advantageous if the asymmetrically designed sections of the closing element springs are primarily arranged in the closing element channel. This results in a good side guidance of the closing element springs, which permits a reliable operation of the compound needle even at a high operating speed.
Further details of advantageous embodiments of the invention follow from the drawing, the description or the dependent claims.